1. Field of the Invention
This invention relates generally to wireless power charging.
2. Description of the Related Art
Most mobile devices use rechargeable batteries as their main energy source. The conventional way to recharge a rechargeable battery is through a wired charger which transforms alternating current (AC) power from mains electricity into suitable direct current (DC) power for charging. However, a wired charger typically requires a cable and two connectors: one to connect to the mains electricity and another to connect to the device being charged. If a user has many devices using different types of wired chargers, the mess of cables and connectors can become inconvenient and unsightly.
An alternative to wired chargers is wireless charging. In a typical wireless charging system, power flows wirelessly from a transmitter to a receiver. The transmitter has a coil(s), the receiver has a coil(s) and power is transferred due to coupling between the two coil systems. The transmitter and receiver are typically compliant with a specification (often, a published standard), so that they will work with each other and with other compliant transmitters and receivers.
Currently, although there is some standardization effort trying to harmonize different wireless power specifications in order to make transmitters and receivers interoperable, there are still multiple incompatible specifications for wireless charging systems. That is, a transmitter compliant with specification A will not operate efficiently with a receiver compliant with specification B. Two common specifications are the Qi standard by the Wireless Power Consortium (www.wirelesspowerconsortium.com) and the Rezence standard by A4WP (www.rezence.com). The drawback of having a large number of different types of wired power chargers is not significantly relieved by wireless power charging, if wireless power charging also requires a large number of different types of chargers.